In this interview, Dr. Priya Perumal from the University of Oulu shares how her team is transforming lithium mine tailings into valuable construction materials. She discusses their work in EXCEED’s WP3, combining experimental research and machine learning to unlock circular, low-impact pathways for Europe’s emerging lithium industry.
Dr. Perumal’s research background
Dr. Perumal’s primary research focus is on up-cycling industrial and mining side streams into sustainable construction materials, thereby addressing the depletion of natural resources and enabling a circular economy in the built environment. Specifically, her work includes enhancing the reactivity of mine tailings for use in binders, ceramics, and fine aggregates; recycling demolition concrete (especially fine fractions) into secondary raw materials; and exploring CO₂ sequestration, indoor/outdoor eco-material interactions and circular construction methods. As leader of the research group Sustainable Construction Materials and Applications at the University of Oulu, she heads a multidisciplinary team of about 15 researchers working on pre-treatment of industrial residues (mechanical, chemical, thermal, carbonation) and incorporation into binder systems (supplementary cementitious materials, alkali-activated materials, ettringite binders) as well as lightweight aggregates and fine-aggregate replacements. The group also investigates full life-cycle assessments, durability in harsh (including arctic) conditions, and pilot-scale industrial applications of the materials.
Interview
1. What are UOulu’s main research interests/objectives in EXCEED? And how do they connect to critical raw materials or circular economy themes?
UOULU is leading Work Package 3 (WP3) of the EXCEED project. The main objective of this WP is to valorise the residual and industrial side streams (or process waste) generated during lithium extraction from hard-rock deposits in Europe. This approach strongly supports the circular economy concept, as the most valuable outputs of lithium mines may extend beyond lithium itself. By recognising and utilising other side streams as secondary raw materials for the construction industry, we ensure that nothing is discarded, what is considered waste in one industry becomes a valuable resource in another. In this way, WP3 contributes to establishing a truly circular material flow within the raw materials sector.
2. We’d like to discuss your latest EXCEED publication “Exploring the potential of lithium tailings in construction materials” in Minerals Engineering, which explores innovative ways to valorise lithium mine tailings. Could you briefly describe what motivated this study?
While doing the characterisation of the side streams supplied from the three prospective mining companies in the project, we needed to explore the promising applications.
WP3 proposed to check the application for Ceramics, alkali-activated material (AAM), Supplementary cementitious materials (SCMs), and Lightweight aggregate as a high-value application. Hence, experimental characterisation was a must to do the job. However, to validate the suggested promising application, there was limited literature on lithium tailings reuse for the proposed application. Therefore, it was decided to look for literature that used some side-streams reuse for these applications and a database was developed, which was large enough to be analysed manually for which used standard ensemble machine learning model was used for training the model, and then the trained model was used to predict the potential use in these targeted applications. The inferences coming out from the experimental study and ML model helped us plan this study.
3. How were the lithium tailing samples selected, and what makes these materials particularly interesting for reuse?
Lithium tailings used in this study were the tailings from the industrial partners involved in the project. The tailings were from different stages of extraction involving flotation, gravity separation, desliming, magnetic separation, and dense-medium separation. The mineralogy, chemical composition and non-hazardous nature in the leaching test of the tailings were the main criteria that made these tailings interesting for safe reuse. The core objective of this WP was to valorise the tailings, supporting circular and zero-waste mining. In this study, all the tailings supplied were considered.
4. The paper investigates different reuse pathways — such as alkali-activated materials, supplementary cementitious materials, lightweight aggregates, and ceramics. Could you explain what these applications are and why they were chosen?
The overall concept of Alkali-activated materials uses alkaline solutions to activate reactive alumino-silicates, producing binder systems with low CO₂ emissions. Supplementary cementitious materials partially replace Portland cement, improving sustainability while enhancing durability. Lightweight aggregates are produced through thermal bloating of suitable tailings to create low-density particles for structural and geotechnical uses. Ceramics rely on alumino-silicate compositions suitable for sintering into tiles or structural products. These tailings can be explored for several other applications as wee. However, these four pathways were the proposed task for the EXCEED project.
5. Your analysis included both experimental characterization and machine learning modelling. How did these two approaches complement each other?
The experimental characterisation and machine learning modelling complemented each other by combining the material characteristics with predictive data-driven support. The experimental analysis provided detailed insights into the chemical, mineralogical, physical, hydration, and environmental characteristics of lithium tailings, confirming its technical viability for reuse. Thereafter, the ML model used the measured properties to sort the tailings into the most promising application. By combining real laboratory data with data-driven prediction, the study achieved a deeper, more reliable understanding of tailings behaviour and identified the most promising valorisation pathways.
6. Which finding surprised you the most in the results?
All these applications require reactive mineral phases. However, amorphous phases were very limited both in our laboratory studies and in the literature. Despite this, the literature still suggested possible applications without reporting the amorphous phases present in the side streams used. Ideally, these studies would have included detailed reporting of the amorphous phases, and this limitation has been highlighted in the manuscript.
7. Based on the study, which reuse route seems the most promising for lithium tailings — and why?
In this study, based on the combined experimental evidence and machine-learning predictions, supplementary cementitious materials and ceramic materials emerge as the most promising reuse routes for lithium tailings. Their high alumino-silicate content, fine particle size (especially M3S and M3M), good thermal stability, low calcium content, and environmentally safe leaching profiles align well with the requirements for SCMs and ceramic production. Additionally, multiple machine-learning models consistently predicted tailings particularly M3S, M3M, and M3D as suitable for these applications, reinforcing their technical compatibility and long-term potential for sustainable, large-scale reuse.
Broader Impact and Relevance
1. What makes this study important in the context of sustainable lithium production and resource efficiency in Europe?
The growing challenge of managing large volumes of tailings generated from hard-rock lithium extraction is directly addressed in this study, making it significant for sustainable lithium production and resource efficiency in Europe. The work shows that European lithium tailings are not waste but rather valuable resources appropriate for a variety of construction applications by offering the first thorough physico-chemical, mineralogical, and environmental characterization of these materials, along with a novel machine-learning prediction framework. This helps the EU achieve its circular economy goals, lessens reliance on virgin raw materials, eases the burden on landfills, and improves the general sustainability and financial feasibility of upcoming European lithium projects.
2. How do your results contribute to the EXCEED project’s mission of enhancing Europe’s resilience in critical raw materials?
The outcomes directly support the goal of the EXCEED project by showing how by-products of lithium mining can be converted into useful building materials, which lowers waste and increases resource efficiency along the vital raw materials value chain. The research supports domestic material recovery, reduces dependency on imported resources, and encourages circularity by demonstrating that European lithium tailings are technically feasible and environmentally safe for reuse, as well as by creating a machine-learning framework to guide their optimal valorization. By making the most of its own mineral resources and guaranteeing more sustainable, accountable, and effective lithium production, this strengthens Europe’s resilience.
3. What are the next research steps — are there plans to validate these results at a larger (e.g., pilot) scale?
Not just based on this study, WP3 partners, including the University of Lorraine, Wienerberger, and Betolar, have significant evidence supporting these proposed applications based on their lab study. Wienerberger will carry out semi industrial scale production of ceramics, and Betolar will carry out semi-industrial production of AAM and SCM incorporating lithium tailings based concrete in collaboration with WP 5 of the EXCEED project.
Personal and Collaborative Aspects
1. How was the collaboration among partners in this study — did you work closely with other EXCEED researchers or external institutions?
In this study, collaboration was extremely integrated and involved close communication with several EXCEED partners. Three potential mining projects in Europe provided lithium tailings, and each partner offered complementary skills ranging from chemical analysis and mineral processing to ceramics, lightweight aggregates, and data-driven modeling. In order to prepare, characterize, and interpret the samples, Geological Survey of Finland, University of Lorraine, Wienerberger, Betolar, and Oulu Mining School were all crucial.
2. What advice would you give to early-career researchers working in critical raw materials recovery or waste valorisation?
Critical raw materials recovery and waste valorisation necessitate multiple perspectives, so I would encourage early-career researchers to embrace interdisciplinary thinking and actively seek collaboration across geology, materials science, environmental engineering, and data science. Gaining proficiency in both experimental characterization and data-driven analysis is crucial because integrating these methods produces more profound understandings and significant results. Research stays relevant and scalable when it stays close to industry and real-world problems. Lastly, keep an open mind because there is unrealized potential in many waste streams. Making significant contributions in this quickly developing field requires curiosity, perseverance, and a circular economy mindset.
